Comments on the Special Issue of Communications in Statistics (Volume A8, Number 10) Concerned with Weather Modification Experiments

REPORT DOCUMENTATION PAGE READI:-;STRtlCTIONS
BEFORE CO~IPl.ETlNG FORM
Jerzy Neyman
,. PER~QR"'NG ORGA"I >;AT'Q" "A"E ANO APORESS
Statistical Laboratory
Universit.y of California
Berkeley, CA 94720
Office of Naval Research
Washington, D.C. 20014
ONR NOOO 14 75 C 0159
\2 REPQRTOATE
November 1979
This document has been aporoved for public release; its distribution is
unlimited.
Slanted and unreliable
Weather modification technolo9,y
Tasmania exoeriment
Israeli exoeriment I
~<:.-. rc_'=' _,.,.."••in Il~.<......,. _'d"""F &y &I~<' nu_h.)
As stilted by the Editors of the Speciill Issue, it was cOfl'piled with reference
to two of my statements; (1) that ~uch of the current weather modification
literilture is slanted and unreliable, and (2) that progress in the building'of
a reliilble weather modification technolo9Y reouires an interdisciplinary study
of as many completed cloud seedinq exoeriments as possible. The material pub~
lished in the Special Issue relates to two completed exoeriments, the Tasmania
and the Israeli exoeriments. It is shown that a realistic appraisal of a
DO \~~"n 1m EO'TlONO"'''QV6~'&08's.oLETE UNCLASSIFIED (ConL)
20. (Cont. from reverse)
cOl!'Pleted experiment requires a orolonged effort, including an examination of
quite a few relevant piA:llications and, on occasion, sore nur.tJerical worle on
published raw data. It aopears that an interdisciolinary reanalysis of the
TaSMania experiment can contribute to the development of a reliable cloud
seedi n9 techno1oro'.
1. INTRODUCTION
The contents of the special issue of Corrmunications in Statis­tics
(Vol. AB, No. 10, 1979) edited by J.J. Wiorkowski and P.L. Odell
(i) Preface by the Editors, pp. 953-954.
(ii) LJ. Smith, "An experimenter's view of the application of
statistics to cloud-seeding experiments," pp. 955-973.
(iii) K. Ruben Gabriel, "Some statistical issues in weather mod­ification,"
pp. 975-1015.
(iv) A.J. Miller, D.E. Shaw, loG. Veitch and E.J. Smith, "Ana­lyzing
the results of a cloud-seeding experiment in Tasman­ia,"
pp. 1017-1047.
As correctly stated by the two Editors, the idea of a special
issue originated from their conversations with Donald B. Owen and
myself. At the time, I expressed my concern about inconsistencies
abundant in the cloud-seeding literature. However, the nature of
these inconsistencies is not illustrated in the special issue and
the reason for my concern is not explained. I note that the "spe­cial
issue was compiled so that. .. the statistics corrmunity could get
relevant information and insight into the very difficult •.• " domain
of "weather modification experiments."
The purpose of my present "corrrnents" is to help to achieve this
insight. A few illustrative examples are likely to be useful.
2. NATURE OF "INCONSISTENCIES"
AND· REASONS FOR MY CONCERN
The following passages are quoted from the first column of my
review article (Neyman, 1977a). The title of the article is "A
statistician's view of weather modification technology." My focus
was on the following three questions:
"Question i. Is the present cloud seeding technology reliably
confirmed as a means of alleviating drought?
~:No.
Question ii. Is there evidence that cloud seeding affects pre-
cipitation and, if so, what are the indicated effects?
Answer; It appears established that cloud seeding does
affect precipitation and does so over areas far in excess of
the intended targets, occasionally up to distances on the order
of hundreds of k.ilometers. In some cases the effects are large
increases and in some others large decreases in precipitation.
The several hypothetical Il'.echanisms advanced to explain these
effects and to predict them vary in their empirical support and
convincingness. In particular, much of the existing literature,
some of it stemming from official sources, is SLANTED AND UNRE­LIABLE.
[Here caps are added. The emphasized words correspond
to the "inconsistencies" mentioned by Wiorkowsld and Odell.]
Question iii: What are the means of advancing the development
of a reliable weather modification technology?
Answer: Establishment of at least two philosophically differ­ent
interdisciplinary research groups, including statisticians
versed in experimental work. .•..with a special mission to reeval­uate
the data of as many already performed cloud seeding exper­iments
as possible, ~ continuation of properly planned exper­imentation.
The suggested research groups should have unlimited
access to the same data and have facilities for personal meet­ings
"to exchange ideas. They should be funded from sources
other than those engaged in funding cloud seeding."
I should have added that reevaluations of completed experiments are
tedious and time-consuming. Thus, to achieve reliable results, the
work. of the recorrrnended at least two interdisciplinary research
groups should be planned for several years.
My point is that, soon after the pub1icatio'n of my review there
appeared a two-volume document, The Management of Weather Resources
(Cleveland, 1978). To my regret, the work. sUlmarized in this docu­ment
was done in a hurry and was not quite "interdisciplinary."
The first volume of the document represents a report of the Weather
Modi fi cati on Advisory 80ard appoi nted by the Secretary of Corrrnerce
and the second that of the Board's Statistical Task Force. The two
groups worked under ;lressure to complete the studies within about a
year. The lack of harmonious interdisciplinary effort is reflected
in the FOREWARD to Vol. 11 written by Harlan Cleveland. Chairman of
the Advisory Board. Here the following statement appears relevant:
MThe Board's own judgments do not always follow the statistical
findings to their ultimate inconclusiveness ..
The following quotation fmlll page B-8 of the Statistical Task
Force report seems to reflect both the lack of interdiscipli':lary
effort and the time pressure:
Tasmania
This study depended very heavily on control
areas to !>rovide precision of results. Seeding
was interrupted -- or aborted -- whenever wind
directions suggested that Agt nuclei might be
conveyed directly toward a control area. (Since
such days were still counted as "seeded days," no
false significances would result.) In view of the
limited area offered by the interior of this large
island, remote-effect issues must. we feel, be
taken seriously. We do not feel cOl!lPetent to ad­equately
evaluate them here.
In the following pages there are described Minconsistencies"
of two different kinds. both occuring in the Wiorkowski-Odell
spedl issue No. 10. The focus is on two experiments, the Tasman­ian
and the Israeli experiments.
3. INTERFACE BETWEEN THE WORK OF WEATHER t()OIFICATION
EXPERIMEHTERS AND THAT OF STATISTiCIANS
The title of this section is based on a sentence in the Intro­duction
to the article by LJ. Smith (pp. 955-973), under the inspir­ing
title MAn experimenter's view of the application of statistics to
cloUd-seeding experiments." The spirit of the article seems to be
properly sUllITlarized by the dictum that "both the statistician and ex­perimenter
are searching for the truth as to what the cloud seeding
does. "
I fully agree with this spirit, but must suggest a change in
the fonnulation of the dictum. r~y preference ;s for the following:
"both the statistician and the experimenter OUGHT to search for the
truth as to what the cloud seeding does."
Unfortunately, such an interdisciplinary cooperation does not
always occur with the result that "much of the contemporary litera­ture
... is SLANTED AND UflRELIABLE."
While the motivation for cheating is, clearly, some personal
gain, the means used by particular experimenters may be complicated.
In fact, it may be subconscious. From the point of view of the
development of a reliable weather modification technology, the fol­lowing
passage from (Neyman, 1977a) is relevant:
RELIABLE INFORAATION ON EFFECTS OF
CLOUD SEEDING MAY RESULT FROM STRICTLY
RANOOHIZED EXPERIMEtrrS
With reference to precipitation augmentation, the
essence of a randomized experiment is, briefly,
as follows:
"se:~~~~'o~~~~~~~~~e~~~e~~~~:l-~~~~~;e(~~riable-are
clearly defined. In the simplest case, the po­tential
experimental period may be of fixed duration,
say 24 hr from 0730 of a gi ven day to 0730 of the
next. In this case, the response variable might be
the precipitation measured by specified gauges (de­fining
the "target"), say from 0800 of the given day
to 0800 of the next.
A special organizational unit, to be called the
"randomization center" (RC). must be established.
At an appointed time before the beginning of a po­tential
experimental period, the experimenter re­ports
to the RC whether the approaching potential
experilnental period is suitable for inclusion in the
experillll2nt -- that is, whether it is to become an
"experimental unit. - In the affirmative case, the
experimenter comnunicates to the RC certain other in­formation
deemed imoortant, such as the nature of the
prevailing weather (type A, type a, or type C, etc.).
In response, the RC provides the experimenter with a
randomized decision, either a permissive "seed" or a
categoric "do not seed." It is emphasized that the
randomized decision must be comflRJnicated to the ex­perimenter
AFTER his declaration as to the approaching
experimental unit, not before. In fact, it would be
best to arrange that even the personnel of the RC
have no advance information on the nature of the forth­comi
ng randOl!lized decision. Perhaps, a computerized
random nUl'Jt)er generator could be adjusted for this
purpose ....
The primary evaluation of the experiment must be
based on all the experimental units (some seeded
and others not) and no others, and it must use the
originally defined response variable. The supple­mental
information about the type of weather ought
to be used for stratification purposes and is use­ful
by providing the experil!'lenter with lreans to
verify his ideas.
The reader will realize that the spirit of the above passage
is fully consistent with Dr. Smith's idea that "both the statistician
and the experimenter are searching for the truth as to what the cloud
seeding does."
As ell19hasized by Smith, the experimenter has a specific field
of competence "in subjects suchas physics, meteorology" [perhaps,
also] "aviation and engineering.- The type of experiments contem­plated
by Smith is exemplified by the Tasmania experiment analyzed
by Miller !!....!.!.' p. 1017 1n the same issue of COJIIDunications in
Statistics. The object "of the experiment is to find out if seed­ing
cloudS with ice nuclei can increase the rain MEASUREO OVER A
DESIGNATED TARGET AREA [emphasis added]. Time is divided into .per­iods
[which I shall assume to be one day] on some of which selected
at random, seeding takes place ... " The statistician is expected to
analyze the data reliably, in order to answer the questions of the
experimenter and, possibly, also those of his "customer" such as a
hydro-e1ectri c author; ty.
Quite rightly, Smith is uneasy about the assumptions underlying
the statistician's work. "The objective ought to be to avoid the
use of any assunption unless there is good evidence that it is
acceptable." I fully agree. Specifically, a statistician's "reli­able
assumptions" are proved theorems, such as the law of large num­bers,
the central limit theorem, etc. Provided there are no mistakes
in the deductions, the conclusions drawn using such theorems wilT be
reliable (Neyman, 1979a).
My own concern is that, in addition to hypotheses underlying
the work of the statisticians, there are also hypotheses adopted by
the experill'lentalists. Are they always realistic? Here is an example.
At the end pararaph of Smith's Introduction there is the follow­ing
outline of a proposed method of analyzing the data of a randomized
experiment:
For each seeding day the ll'lE'asured tarQet area
rainfall is compared with an estimate of the
rain that would have fallen in the same period
if seeding had no effect. This estimated rain
is derived from covariates which usually include
rain in adjacent control areas in both seeded
and unseeded periods. (In simple experiments
the measured rain in a control area may be used
as an estimate).
It is here that I see a contradiction between the opinion of
Dr. E.J. Smith and my own. It seems to me that the methodology in­dicated
by Smith depends upon an unverified hypothesis, a "meteoro­logical"
hypothesis, that seeding over the designated target does
not affect the rainfall in the adjacent control area. Otherwise,
-the measured rain 1n a control area" during a seeding period would
not be an appropriate estimate of the target rainfall "that would
have ,fallen in the same period if seeding had no effect. II
In full confonnity with Smith's own suggestion that -the ob­jective
ought to be to avoid the use of any assulTlltion unless there
is good evidence that it is acceptable," I feel in need of an effort
at verification.
How can one check, at least tentatively. whether the ass~tion
that the rainfall in a control area is not affected by seeding over
the target? How can one do so without relying on any other unveri­fied
asswnption? The only answer seems to be: examine the totality
of published experimental data and produce a sUlllllary.
The data on the Tasmania experiment we have were published two
years ago (Smith!!....!!.. 1977). There are two sets of data. Both
give average rainfall arr(lunts in the intended "target" and in four
other areas in Tasmania. Three of them are described as "controls"
and the fourth as the Eastern Subsidiary Area, see Figures land 2.
The precipitation amounts are means per raingage, per "period."
The particular perioe's varied in length, from about ten to eiohteen
days. As i ndi cated in the above quotat; on from the report of the
Statistical Task Force, there were some irregularities.
One set of data refers to four years 1964, 1966, 1968 and 1970
which were the experimental years, with seeding over the target dur­ing
randomized periods. The other set of data refers to years 1965,
1967 and 1969 during which rainfall amounts were measured in all the
five areas but there was no seeding. We may label these years, the
"control years." The purpose of the three "odd" control years inter-mingled
among the four "even" experimental years was to check the
hypothesis, again a meteorological hypothesis, that the seeding dur­ing
a particular year can affect the precipitation during the subse­quent
year, the so-called "presistence" hypothesis.
The attempt at an objective sunmary of all the publlsbed precip­itation
data resulted in Figures 1 and 2. Both show the map of Tas­mania,
including the target and four other areas mentioned. The
Stat. Lab's contribution is limited to percentages attached to each
of the areas of interest. They represent what I like to label "per­cent
effect" of seeding, namely 100[{S-NSl/NS]. Here Sand NS repre­sent
the mean measured rain in the given area that fell during the
periods with and without seeding, respectively.
Figure 1 corresponds to the four experimental years, 1964, 1966,
1968 and 1970. It is seen that the percent effect in all the five
areas is negative. The least seed period deficiency of rain, namely
8%, was found for the target and for the "South Control" area. The
greatest seed period deficiency was found for the North Control. It
amounts to 21%, more than double that for the targetl The deficiency
of seed period rain for all the areas corrbined is 15%, a finding
likely to be of interest to the hydro-electric authority.
What is convincing and what is not is a subjective matter. In
my own opinion, Figure 1 fails to support the assumption that seeding
over the target does not affect the rain over the North Control. If
anything, it seems to support the idea that seeding by methods com­parable
to those in Tasmania can have far-away effects that are strong­er
than those in the target. See Section 2 above.
LOCATION OF TARGET
AND CONTROL AREAS
Roinoouqee
Airport t:.
o NOUljC;~ Mile$40
~:"':~,
NORTH- eORTHCONTROL co'%1lbl· -:.: A2R!~A AREA •• ". Lounceston
-14% •• EASTERN
TARWET SUBSIOlARf
42" ~:iA ••: ~ •• ~;5~o ..- ...
145" 148"
FIG. 1. Relating to experimental years.
LOCATION OF TARGET
AND CONTROL AREAS
FIG. 2. Relating to control years.
Here. with some feeling of regret. I must mention II point relat­ing
to the statistical team that cooperated with Or. Smith in the
evaluation of the Tasmania experiment. As indicated on p. 1021,
the team used the "dolble ratio statistic," because it "has an intu­itive
appeal." The reader will have no difficulty in noticing that
this "intuitive appeal" depends very much on the unYeri fled "meteor­ological"
hypothesis that the seeding over the target does not af­fect
the rain in the control. In particular, if the effects of seed­ing
on rain in the target and in the control /Ire both negative and
if the negative effect in the control is stronger than in the target
(as in Figure 1), then the double ratio statistic will lead to II
misleading conclusion.
It seems to me that the selection of a test statistic merely
because of an "intuitive appeal" is not an inspiring procedure. The
roore challenging way is to formulate sorr.e intelligible optimality of
the needed test criterion and to DEDUCE the needed formula (Neyman.
1979a).
Figure 2. analogous to Figure 1. illustrates the precipitation
pattern in Tasmania that prevailed during the three control years.
when there was no seediny. Here. the "percent effects" were calcu­lated
for·what may be labeled "placebo seeding." As mentioned. the
ptblished data give the rainfall alOOunts for consecutive periods.
The succession of "placebo seeding" was arranged to coincide with
the succession of real seeding for the experirental years. It is
seen that the patterns of rainfall exhibited 1n Figures 1 and 2 are
very different. Is this difference causally related to seeding dur­ing
the experimental years and to the absence of seeding during the
controls? Not necessarily. It R"lay be due to rrr; mistak.en allocation
of "placebo seeding" during the control years.
The essence of the presistence hypothesis seems to be that.
whatever the effect of seeding in a given year may be. this effect
"persists" over several months of the next year with a gradual decay.
Here we face a difficulty that seems even greater than that in the
establishment of the phenomenon of the far-away effects of local
10
seeding. The point is that the possible "persistence" effect is
confounded with faMiliar seasonal variation in precipitation. In
very general terms, the Berkeley area has two rainy periods, of
about one month duration. One, a mild one, occurs in October­Novemer,
and the other, stronger one, begins about the middle of
January. Naturally. the intensity of these rainy periods varies
considerably from year to year.
4. ILLUSTRATIONS OF FAR-AWAY APPARENT
EFFECTS OF LOCAL SEEDING FOUND ELSEWHERE
During our more than a quarter of a century of interest in
weather modification, it was natural for our Berkeley group to
study the reliability of experimental designs that were corrmonly
used. This included the cross-over design and the design using
control areas. We found them both unreliable. The relevant ques­tion
was whether the seeding over the designated target can affect
the rainfall over a distant area.
Experilrents suitable for studying this question are those of
long duration, with a properly randomized design of seed/no seed
over a designated target and with a "natural" experimental unit of
24 hrs, morning to morning. Here, the word "natural" refers to the
periodic changes in temperature, etc., connected with the irradiation
from the sun. The additional requirements refer to the availability
of data on wind directions and on hourly precipitation data.
Our studies included three experiments: (1) the Swiss experi­ment
Grossversuch III, (2) the Whitetop experiment of Professor R.R.
Braham performed in Missouri, and (3) the Arizona experiment performed
by Professor Louis J. Battan. To my regret (Neyman, 1979b), a closer
study of the Whitetop experilrent indicated some difficulties with
randomization. For this reason, the findings described below refer
to two experiments only, the Grossversuch III and the Arizona exper­iments.
The details of the work are somewhat voluminous (see refer­ences
quoted below) and the following brief SUrMlaries must suffice.
The far-away effects of local cloud seeding werE:' first studied
for the Swiss experiment Grossversuch III (Neyman ~, 1969).
11
Here, the target was the canton T;eino on the southern slopes of
the Alps. The studied far-away localities included two areas in
Switzerland in which we had reliable data from 20 gages each. One
area was near Z'urich (some 80 miles away) and the other near Neueh­atel
(some 120 miles away). The average apparent effects of seeding
on all the 190 days with "stability layers" were as follows:
Table I
Apparent effects of seeding at Grossversuch III
on days with stability layers
12
Area
Tieino
Zurich
Neuchatel
Percent Two-tail
Effect Significance Probability
+£4 0.031
+67 0.012
+57 0.037
As mentioned, Table r refers to all the 190 days, irrespective
of the prevailing wind directions. The followin9 Table II gives sim­ilar
data for the 94 days when the published winds had a southerly
velocity component. This stratification was performed because of the
information that the primary source of atroospheric humidity in Swit­zerland
is the Mediterranean, in the south.
Table II
Apparent effects of seeding at Grossversuch III
on days with stability layers and southerly winds
Area
Ticino
Zurich
Neuchatel
Percent Two-tail
Effect Si gniti cance-Probabil ity
+102 O.OlB
+116 0.004
+ 64 0.060
In interpreting this table one must remerrber that Zurich is al­most
directly north of Ticino while Neuchatel is substantially to the
northwest. Here, then, the degree of "downwindedness" was crude,
which stimulated the development of a new methodology, the moving
grid methodology (Lovasich ~. 1971).
Curiously, the apparent effects of seeding on days with uninhib­ited
updrafts were all negati ....e. but none significant by customary
standards. The subsequent use of the moving grid methodology clari­fied
the situation. The original measurement of the degree of down­windedness
was too crude. Our final finding was a 61: average defi­ciency
of seeded day precipitation in localities 90 to 180 miles down­wind
from Tieino. with a two-tail significance p" 0.002.
The above findings for Grossversuch III were unexpected and stim­ulated
our interest in the question of the generallty of the phenomena
observed. It is this question that rot'ivated our persistent'studies
of the Arizona experiment performed by Professor l.J. Battan. The ex­periment,
with two "programs." included 212 experllllental days. Profes­sor
Battan's target was an isolated body of Santa Catalina Mountains.
The seeding was conducted over2-4hours beginning at about 12:30 p.lIl.
Battan's own evaluation was based on rainfall during 5 hours only. from
1 p.m. to 6 p.m. Our reevaluation used 24 hour rainfall from noon to
It included not only the Santa Catalina Mountains but also a
locality. Walnut Gulch. about 65 miles to the south soutbellst from the
Santa Catalinas. Here. the Water Conservation Research Division of
the Agricultural Research Service maintains a very tight set of re­cording
rain gages. The person in charge is Dr. Herbert B. Osborn.
It appeared that during the Arizona experiment there were 26 gages
that operated reliably. Table III surtrnarizes the results obtained
(Heyman!!.....!!.. 1972).
Table III
Apparent effects of seeding at the Arizona experiment
13
locality
All Davs
Percent Two-tail
Effect Probability
Walnut Gulch Downwind
Percent Two-tail
Effect Probability
Santa Catalina
Walnut Gulch
-30
-40
0.06
0.02
-9
-73
0.78
0.01
It ;s seen that both parts of Table III indicate the apparent
effects of seeding over the Santa Catalinas on the 24 hour rain at
Walnut Gulch are stronger than in the intended target. Also. the
significance of these effects is rrore impressive.
The timing of these apparent far-away effects is of interest
(Neyman, 1977a). It is illustrated in Figures 3 and 4.
FIG. 3. Diurnal variation in hourly rainfall in Zurich when it was
approximately downwind and when it was approximately upwind
from Tieino. Solid lines correspond to days with seeding;
dashed lines to control days.
ii 4. T,_.",
FIG. 4. Diurnal variation in hourly rainfall in Walnut Gulch when it
was approximately downwind and when it was approximately up~
wind from the Santa Catalinas. Solid lines correspond to
days with seeding; dashed lines to control days.
It would he J!()st interesting to see whether the "downwind/up'Hind"
differences illustrated in Figures 3 and 4 were also observable during
the Tasmania experiment. The difficulty is that 1n Tasmania the exper­imental
periods were rather long, presumably with very variable wind
directions, with varying wind velocities, etc.
14
5. COMPARISON WITH THE ISRAELI EXPERIMENT I
It is my opinion that the Tasmania experiment, as dt!scribed in
the Wiorkowski-Odell special issue of COrM1unications in Statistics,
and especially as described in the Final Reoort (Smith ~. 1977).
;s a very valuable contribution to the weather modification litera­ture.
The reason is that the material published includes many de­tails
about the facts that happened, the facts relevant to Dr.
Smith's question about "what the cloud seeding does." r wish I
could express a similar opinion on the Israeli experiment. This
applies both to the original evaluation (Gabriel, 1967) and to Pro­fessor
Gabriel's article in the Wiorkowski-Odell special issue now
discussed. The following passages, marked A and B, are quoted from
this article.
A. Page 983.
Pemaps one reason for the surprisin9 success of the two
Israeli experiments is that expertise in cloud physics
was closely involved in all stages of design, evaluation
and analysis (Gabriel, 1967; Gagin and Neumann, 1976).
In the existing uncertain state of the art, we cannot
afford to do without the very best available experts.
B. Page 977.
In the first Israeli experiment (Gabriel, 1967), the ex­perimental
unit was a 24-hour period, STARTING AT 8 AND
ENDING AT B on the next day. (1) Randomization was applied
to calendar dates and ...
The reader will notice that the above capitalized description
of the experimental unit is not complete. The hour 8 may be B a.m.
or B p.m. The following passages, marked C and D, are quoted from
Professor Gabriel's article, described as (Gabriel, 1967).
C. Title Page.
THE ISRAELI ARTIFICIAL RAINFALL
STIMULATION EXPERIMENT.
STATISTICAL EVALUATION FOR THE
PERIOO 1961-65
K.R. Gabriel
Hebrew University, Jerusalem
15
1. Introduction
A rainfall stimulation experiment is being carried out
in ISrael by silver iodide seeding from an aircraft in a
randomized crossover design. The operations are directed
by Electrical and Mechanical Services (Mekorot, ltd.),
Mr. H. Cohen, Director, and are financed by the Israeli
Ministry of Agriculture. The experiment is conducted
under the guidance of the Rainfall COll1llittee whose chair­In3n
is Professor LD. Bergmann, and the related research
work. is performed at the Hebrew University, under the direc­tion
of Professor J. Neumann. THE AUTHOR IS RESPONSIBLE FOR
THE STATISTICAL DESIGN AND EVALUATION, Daily rainfall data
are provided by the Israeli Meteorological Service from its
regular network of raingage stations. [Emphasis added.]
O. Page 94. Table specifying the experimental units on which
the evaluation was based.
TABLE II
~ITS EMPLOYED IN THE EXPERIMEKT
Season Date Period Unit of Time
1961 half 19. 2.61-15. 4.61 weekly 0000 to 0000 hrs
15.10.61- 5.11.61
1961-62 7.11.61-15. 4.62 daily 2000 to 2000 hrs
1962-63 16.10.62-15. 4.63 daily . 2000 to 2000 hrs
1963-64a 1.11.63- 8. 1.64 daily 2000 to 2000 hrs
1963-64b 9. 1.64-lJ. 4.64 daily 0000 to 0000 hrs
1964-65 16.10.64-15. 4.65 daily 0800 to 0800 hrs
Here the specification of the experimental units is complete.
H"""ever, it is indicated that the actual units varied. For a brief
period the unit was 8 a.m. to 8 a.m. Then, for a longish period, it
was from 8 p.m. to 8 p.JIl. Then there was a return to the original
8 a.m. to 8 a.m. This description generated some literature.
1 felt impressed by the variability of the experimental units,
and when writing a historical review (Neyman, 1977b), expressed the
opinion that the design and the evaluation used are "unprecedented."
Next year there appeared two protests (Gabriel and Neumann, 1978) and
(Mielke, 1978). Here it is relevant that Or. Hielke, a Professor of
Statistics, is at least partly responsible for the evaluation of the
cloud seeding experiment known as Climax I. This evaluation is also
mentioned in (Neyman, 1977b).
16
17
Here, I wish to refer to the statement by the Editors Wiorkowsi­Odell
that their Special Issue was complied so that the statistics
cOFmlunity could gain insight into the complexities of weather II"()difi­cation
studies. My suggestion is that interested rrembers of the sta­tistics
cOlMlunity examine the publications mentioned in the preceding
paragraph. In fact. I wish to suggest one IOOre paper (Hobbs and Rang­~~.
This paper ends with the following sentence:
"In view of the irrportance that has been placed on
the Climx results, an independent evaluation of the
statistical results of these experiments is urgently
needed. "
My question is: Why only of Climax?
ACKNOWLEGEMENTS
This article was prepared using the facilities of the Statistical
laboratory, with partial support from the Office of Haval Research,
Contract No. ONR NOOO14 75 C 0159, and the DepartlU!:nt of the Amy,
Grant No. OA AG 29 76 G0167. All the opinions expressed are those
of the author.
BIBlIOGARPHY
Cleveland, Harlan (1978). The ManagelU!:nt of Weather Resources,l, Pro­posals
for a National POllCY and Program, Report to the Secretary
of COllJl1erce from the Weather Modlftcatlon Advisory Board (Harlan
Cleveland, chairman); II, The Role of Statistics in Weather Re­sources
Management, Report of the StatlsticaJ task Force (JOhn W.
lukey, chainnan) to the Weather Modification Advisory Board.
Washington, D.C.: U.S. Government Printing Office.
Gabriel. K.R. (1967). The Israeli rainfall stilllulation experiment,
statistical evaluation for the period 1961-65. Prot. Fifth Berke­lev
SYIIlJ). Math. Stat and Prob., ::!..' "'leather Modlflcation (luclen
Le Cam and Jerzy Neyman, editors). Berkeley: University of Cal­ifornia
Press, 91-113.
Gabriel, K.R. and Neumann, J. (1978). A note of explanation on the
1961-67 Israeli rainfall stimulation experirrent. J. Appl. Meteor.,
.!l.552-554.
Hobbs, Peter V. and Rangno. Arthur L. (1979). COn'll'lE!nts on the Climax
and Wolf Creek Pass cloud seeding experi~nts. J. App1. Meteor.,
.1!. 1233-1237.
Lovasich. J.l. , Neyman, J., Scott, E.l. and Wells, M.A. (1971).
Further studies of the Whi tetap cloud seeding experiment. Proc.
Nat'l Acad. Sci., §!. 147-151. -
Mielke. Jr., Paul W. (1978). On criticisms concerning the Israeli
experiment. J. Appl. Heteor .• .!l.. 555-556.
Neyman, J. (1977a). A statistici.a,n's view of weather ll'IOdification
technology (a review). Prot. Nat'l Acad. Scf.l!. 4714-4721.
Neyman, J. (l977b). Experimentation with weather control and statis­tical
problems generated by it. Applications of Statistics
(P.R. Krishnaiah. ed.). Amsterdam: North-Rolland piblishing
Co., 1-25.
Neyman, J. (1979a). Developments in probability and mathematical
statistics generated by studies in meteorology and weather mod­ification.
COl'l'l1lun. Statist.-Theor. Meth .• ~. 1097-1110.
Neyman. J. (1979b). COll11lent on Professor Braham's paper "Field Ex­periJrentation
1n Weather Modification." J.A.S.A .• Ii. 90-94.
Neyman J. and Osborn. H.B. (1971). E.... idence of widespread effects of
cloud seeding at two Arizona experiments. Proc. Nat'l Acad.
Sci .• ~. 649·652.
Neyman. J .• Scott. E.l .• and Wells. M.A. (1969). Statistics in rreteor­ology.
Rev. tnt'] Stat. lnst .• E. 119-148.
Neyman. J .• Osborn. H.B .• Scott. LL.. and Wells. M.A. (1972). Re­evaluation
of the Arizona cloud-seeding experiment. Proc. tlat'l
Acad. Sci .• §!. 1343-1352. ----
Smith. E.J .• Veitch. loG .• Shaw. D.E.. and Miller. A.J. (1977). ~
Cloud-Seeding EXJjerirnent in Taslllania. Final Re~rt. Part 1.
~es~;~~ihoSc~~~tti~~ :~dU;~~~st~~~~s ~~e~~J Ig~a~~~~~~~~.Com-
Australia.
18
I am indebted to Professor David R. Brillinger for call iog my
attention to the relatively brief paper by Harlan Cleveland and
for providing me with a copy. Weather lilOdification issues are
complex and, in 11 sense, Cleveland's paper is revealing. It is
likely to be useful not only to the editors W;orko~lski and Odell.
but also to the public at large. Because Cleveland's paper repre­sents
his testiroony before a group of- U.S. Senators, its circula­tion
must be limited. It is reproduced in the present Addendun.
THE 1'IAHAGE.lIIENT OF WEATHER RESOURCES:
Our Need for 11 Pol icy is Now
Testimony of
Harlan Cleveland
Chaiman of the Weather Modification Advisory Board
before the
Senate Corrmittee on Corrmerce. Science and Transportation
SubcollJDittee on Science. Technology. and Space
October 24. 1979
Aspen Institute for Humanistic Studies
Pro9ram in International Affairs
P.O. 80x 2820. Princeton, N.J. 08540
THE "'.ANAG£MEHT OF WE!HHER R£SORUCES:
Our Heed for a POlley lS Row
Testi1T.Onyof
Harlan Cleveland
Mr. Chairman:
1.
In the Hational Weather Modification Polley Act of
1976 (P.L. 94-490 of October 13. 1976). Congress called
on the Secretary of Cor.merce to ~conduct a comprehensive
investigation and study of the state of scientific know­ledge
concerning weather modification technology. the
problems 'impeding effective implementation of weather
modification technology, and other related matters."
The study was ~to develop a comprehensive and coordinat­ed
national weather rodification policy and a national
program of weather modi fi cation research and development.·
Congress asked for a final reoort in one year.
It is now three years and eleven days later. A
part of that time -- a little more than a year of it --
19
was occupied by the work of the Weather Modification Ad­visory
Soard, which was appointed by Secretary of Corrmerce
Juanita Kreps in April 1977. held twelve publ ic hearings
and working meetings in various parts of the United States.
consulted ....ith experts frolll many other countries, and sub­mitted
its final report to the Secretary on July 12, 1978.
This report, entitled The Management of Weather Re­sources:
Proposals for a National Policy and Program, has
of course been aVill lable to the Congress as well, but the
Executive Branch had not until this hearing reacted to the
report or expressed itsel f on the need for a national pol­icy
about efforts to change the weather at hUl!Ian corrmand.
/o':eanwhile two bills to establish a national policy and
authorize a national program have been introduced, S.1644
by Senator Adlai Stevenson and S.829 by Senator Bellman.
You have asked me, as Chainnan of the now~disestab­lished
Weather ~odification Advisory Board, to discuss
these bills. without advance notice of the position, if
any, of the E;.lecutive Branch.
The Advisory Board's report contains a rather full
SUlIJMry and Recommendations. That section of the report
was reproduced in full in the October 1978 issue of the
~~iJe:ifo~:W~~~ ~~~~~~ 7e;=~~i~daih;o6~~~f'b~ig~~:~_
sive administrative history of the Advisory Board and iden­tified
its members. A reprint of this material is attached
to my testimony. Rather than burden my direct testimony
by rehearsing 1n detail the arguments and conclusions in
our Report, I would hope that the SUflIConmittee would be
willing to include in the record of its hearing the text
of this reprint.
II.
I think it is fair to say that the unanimous report of
our Advisory Board is the most comprehensive policy analysis
now available on the subject of weather modification -- or
weather resources management. as we preferred to call it.
It may be helpful to Ilighlight our key findings and propos­als.
First. The benefits likely to be derived fmlll man­agement"
01 weather resources -- for the" distribution of water,
the growing of food and fiber. the production and conserva­tion
of energy, and the warding off of some of the severest
storms -- are out of all proportion to what it will cost to
learn enough about the atmosphere to modi f.v the weather pur­posefully
and prudently.
Second. The prime reouirement of a national policy in
this ~is to learn ll'lOre about the atmosphere itself.
But we know enough already to guess that a IOOch intensified
and steady program of scientific inquiry and field experi­ments
over the next two decades will yield regionally
20
important increases in mountain snowpack in the early 19805,
increased rainfall in areas like our High Plains in the late
19805, and reduced hurricane winds and hail damage by the
19905.
The scientific uncertainties are real. But they are not
a reason for the Federal Goverrwent to freeze in hand-wring­ing
inaction. They are also not a reason for the scientific
. cOl!1llUnity to acquiesce in inaction. If they were, uncer­tainty
would have ruled out the experiments of Galileo, the
explorations of Columbus, and even the speculations of
Heisenberg on uncertainty. The proper attitude toward
scientific uncertainties that stand in the way of large
potential benefits to farmers, city people and dwellers on
hurricane-prone coastlines ;s to get on with a serious
research and develo!Xflent effort that matches the scale and
complexity of the problem. And the key to such an effort. as
we said in our report. is basic research on the physics and
dynamics of the atmosphere itself.
Third. The main weather modification technology. cloud
seediiig'Tilsually with silver iodide), has been used
OPERATIONALLY in 74 countries and is regularly practiced in
the United States. [Emohasis added.] In 1977 clouds were
seeded in 88 projects in 23 states, coverin9 more than a
quarter of a llIillion square miles of U.S. territory. The
Federal Government, working with the states. has to assume
responsibility for making sure that quality standards and
qual Hied people are the rule in weather resources
management.
Fourth. Most "weather modification" so far has been
unint~ the product of urbanization. power production.
cropping patterns. deforestation and irrigation. Learning
roore about the unintended consequences of modern industrial
civilization is an essential part of learning how to change
weather on purpose in ways that benefit people.
Fifth. More and more Americans are moving into hurri­cane
patJi'S; the U.S. migration to the Sunbelt has enormously
increased the populations, property and productive industry
at risk. Even on faVOrable assumptions about warning times.
another storm like 1969's Camille. roving up the sea-level
delta from Galveston to Houston. could cost 10,000 lives and
inundate two-thirds of the U.S. petrochemical industry in a
few hours.
Hurricanes are a triple threat --: from wind, .stonn surge
and flooding. There is an intriguing but not yet proven
theory for moderation of their wind speeds. but it needs a
sustained U.S. research effort and a sensitive framework of
international cooperation. especially to facilitate experi­ments
on real hurricanes in the Western Pacific.
The Weather Modification Advisory Board last year
proposed a lO-year test of hurricane IOOderation, which might
cost S8 to SlS million a year. The recOI:JJlendation is still
21
resting in an Executive pi"geonhole. Do we really need
to have a couple of billion-dollar, kilodeath storms to
spur us fnto doing our scientific and technical homework
on the most devastating kinds of weather?
Shth. Weather resources mani!nernent is, in effect,
a delTIi'e'r"ate "environmental impact;;' so environmental
considerations have to be part of the planning of every
weather apdification try. So does the analysis of eco­nomic
costs and benefits. And so do arranQements for
making sure the affected publics know What-is planned,
and have a chance to help decide what will be done. As
our report says, ~There is no area of public affairs
where a policy of official candor is more integral to
the success of a Government-sponsored research-and-devel­opment
prtlgram. ~
Seventh. The Federal Governn>ent has broad responsi­bilit~
uman intervention in weather systems that do
not respect state, or indeed national frontiers. But
weather resources management is still a very small indus­try,
and we did not propose to lay a heavy regulatory
glove on it. We did make these suggestions:
(a) Each weather management operator should have
a Federal license, as aircraft pilots do.
(b) The Federal Government should take responsibil­ity
for issuing continuously updated, environmentally sen­sitive
·Sound \o,Ieather Resources "'.anagement Practices,"
based on state-of-the-art technology. These would serve
both as a standard to which all Federal field experinents
WOUTd be held, and as guidance for state regulators,
weather resourcemanagers, user organizations such as
farm groups, courts and arbitrators.
(cl The Federal Government should arrange to pro­vide
technical assistance in weather resources managment
to states, local authorities, and private users and oper­ators.
(d) The Federal Government should make clear that
its own operations are subject to claims for damage under
the Federal Tort Claims Act.
~. The United States should actively promote
internatl0nal consultation and cooperation in the field of
weather modification. The benefits of close and candid
consultation are two-way. We want to make sure that our
own programs benefit from the discoveries, insights and ex­periments
of others. And we want to assist other countries
to increase their food, water and energy supplies and limit
their weather damage. To make clear that the U.S. intent
is to prOlll)te the peaceful uses of weather IIX)di fication, our
Advisory Soard also recOfi11lended the earlv ratification of
the EnvirOl'lllental f40dification Convention, a treaty already
signed by the U.S.
22
Ninth. We recomnended a sustained 20·year program of
researcFi""and development, including basic research; refine­ment
of cloud seeding techniques; experiments in the dissi­pation
of stratus; a special effort to learn roore about warm
fog; the study of atmospheric responses to land use, fann
practices, industrial processes and urban 1ife; a special
push to develop techniques for reducing peak winds in
hurricanes; support for the first international cloud-seeding
experiment, now being actively phnned; research on ways
other than cloud seeding to modify local Iveather; research on
impacts -- environmental, economic, and social -- of weather
resource management; and a cooperative Federal/State local
effort to garner maximum scientific knowledge from selected
OPERATIONAL cloud-seeding projects. [Emphasis added.]
The recorrmended R & 0 effort, containing all elements,
would call for Federal appropriations of $37 million in the
first program year (roughly twice the 1977 total of Federal
agency spending for comparable purposes), and increases to
$90 million in the fifth year.
Tenth. The Advisory Board recomnended the consolidation
of alltFi'e Federal GoverlV:lent's weather modification work in
one organization and sufficient autonomy for that organiza­tion
to produce. defend, and carry out a serious and consis­tent
long·term program of research and development .. and
handle the minimal regulatory functions in a highly profes­sional
way.
III.
The members of the Advisory Board were not born yester­day.
We knew how difficult it is in our big government to
"get it all together," how vigorously defended is every
square inch of existing bureaucratic turf. and how hard it is
in every field of public policy to sell integrated and pur­poseful
action to constituencies which perceive a stake in
fragmented action programs. But we were asked to propose a
national policy and program, and we were unan~mous in
concluding that a consolidated program is a must.
I hear tell that even some of the most vigorous
supporters of a serious weather modification effort are now
prepared to settle for a pattern of continued fragmentation.
with some 1im; ted national planning and coordination
attempted through a "lead agency." I believe that this would
be a mistake. "Lead agency" in U.S. federal experience;is a
euphemism for not getting thin')s organized so they are going
to work, yet pretending to do so. "In practice," we said in
our report, "a lead agency generally means telling one part
of the Executive establisl'ment to take charge without placing
in its hands the tools required for leadership."
Our proposal. a deliberately unusual one, was to
establish a small executive board with "a life of its
own" in an existing agency. and an executive director
to carry out the national policy to be enunciated by
Congress; and to bring into the new board's purview,
as its own staff or through contractual relationships,
all the Federal Governl!'!ent's existing and future weath­er
modification programs. This central organization
could and should delegate particular projects to the
agencies best able to carry them oUl; for example, an
experiment such as the bureau of Reclamation's HIPlEX
would logically be entrusted to the Bureau of Reclama­tion
to manage. within the framework of policy and stan­dards
established by the national program office.
Our consensus proposal a year ago was that this
function should be allocated to the National Oceanic and
Atmospheric Administration (NOAA) -- although some mem­bers
of the AdVisory Board would even then have opted for
NASA or even NSF as the host agency. The delay in react­ing
to our report raises -- let us say it frankly -­serious
questions about the capacity of NOAA to take the
kind of vigorous lead that would be required to get a
national weather manage~nt program pulled together and
up to speed.
My own feeling -- the Board has disbanded and I can­not
speak for its rnelTbership ~- is that the earl ier the
consolidation of oceanic and atmospheric functions in one
agency was an enorll'Ous step forward in organizing the
Federal Government for sensible management of resources
in these very special global environments. If NOAA is not
yet the effective center of initiative. Mt yet the enter~
prising and innovative agency it will have to become if it
is to serve our national interest. the proper rel!ledy is to
modify its management. not start stripping it of oceanic
and atJrospheric functions.
IV.
l~eanwhile, in the field of weather resources manage­lTlent,
we are still "taCkl1ng 20~year problems with 5-year
projects staffed by short-term contracts and funded by
one-year appropriations. It is not good enough.· That is
what we said to the Executive Branch more than a year ago,
and that I believe. is still essentially the state of affairs
today. I am therefore delighted that this subconmittee is
moving toward a legislative initiative.
Either of the bills you are considering would represent
a very large step forward from where we are. But as the
corrrnittee writes a bill to present to the Senate. you may
wish to coniline elements of both bills in the final draft.
24
• 5.829, for example. contains in its "Findings"
a rather fuller analysis of the present situa­tion,
and its "Policy" section is closer to the
recomnendations of the Weather Modification Ad­visory
Board. than the comparable formulations
in 5.1644.
• I would hope that the concept of Federal "Sound
Weather Resources Practices· could be a part of
the final draft; the professional quality of
weather resources rnanagel!lent is what will make it
possible to reap large benefits without running
large risks.
• The role of the States, and the need for Federal/
Stale/local cooperation, seems to me an essential
ingredient of a national policy and program;
this is lacking in $.1644 and perhaps not pointed
enough in S.829.
· The licensing of weather modifiers is provided for
in S.1644 but not in S.829; I would strongly re­cOJJlllend
that such a require«ent be retained in
the final bill. as an essential part of quality
control.
· Both bills provide for a board, but in both cases
it i~ advisory; I still think. a small executive
board, in which a few outstanding peoplecourcr­find
a vocation in nursing this potentially impor­tant
field of weather resources management from in­fancy
through adolescence during the next two or
three decades, is an idea worthy of serious con­sideration.
· Even if the board were to be adVisory, I would opt
for the smaller number of merrbers (6 as against lS)
and the longer terms of appointment (6 years rather
than 3), for reasons which do not need to be ex­plained
to any cOlMlittee of experienced political
leaders.
The k.ey functions of our proposed executive board and
its director, or of the Program's Director in the two bills
before you, should be the development of an integrated, roll­ing
five-year program, the management and allocation of the
financial resources which are placed at the disposal of the
national weather lIlOdification effort, and unremitting atten­tion
to quality control in both Federal and nonfederal weath­er
modification. I do urge the subcoJllllittee not to allocate
to a "lead agency" leadership responsibilities without the
administrative authority and budgetary tools to do the job.
v.
In my letter transmitting to the Secretary of COJmlerce
the report of the Weather Modification Advisory Board, in
the early sUl!l1'ler of 1978, I made one CClm1ent that may bear
2S
repeating now that your sub~comnittee ;s moving toward
action.
The history of our time is sprinkled with instances of
new technologies running ahead of the social, economic,
envirorr.:ental, international and institutional thinking
that should accompany them. Precisely because the science
and technology of weather resources Management are still
at such an early stage, there ;s an excellent chance in
this field to do things right •• that is, for policy to
be made and institutions to be bullt in parallel with the
scientific discoveries and technological innovations.
The United States of America does not have a national
policy for the management of \~eather resources. For
reasons spelled out in our report, our Advisory Board
(which was created in response to II Congressional initia­tive)
was una nino us in recor.mending that the time for
adopting II legislative policy stance, back.ing it with II
coherent executive program, and organizing seriously for
a longer term effort, is now.
The following details of the nicely fonnulated ·Testimony· of
Harlan Cleveland attract my attention. In his ·third highlight"
Harlan Cleveland infonns the Senators that "cloud seeding has
been used OPERAT.IOtlAllY [emphasis added] in 74 countries and is
regularly practiced in the United States. In 1977 clouds were
seeded in 88 projects in 23 states."
Again, in his "ninth highlight." Harlan Cleveland calls for a
20~year program ..... to garner maximum scientific k.nowledge frorn
operational cloud seeding projects." Also, he calls for "Federal
appropriations .. roughly twice the total of Federal agency
spending. "
Another point: while Chairman Cleveland found it necessary
to appoint a Statistical Task. Force, the need of statistical
analyses of already completed experiments (as contrasted with
·operations") does not seem to have been eI!lphasized to the Senate
Subconmittee on Science, Technology and Space. The ir.lplication
seems to be that, in the opinion of Chairman Cleveland, the
reanalysis of completed experiments, like the Tasmania and the
Climax experiments, is 1ikely to provide substantially less
"scientific knowledge" than studies of "operational cloud seeding
projects. "
26
Issues related to those discussed by Harlan Cleveland are the
subject of the voll,l'lle Legal and Scientific Uncertainties of
Ileather Modification (Ed .• W. A. Thomas, Duke University Press,
1977). Here, an article by Professor L. J. Battan is of particu­lar
interest. The article's title is -The Scientific Uncertain­ties:
A Scientist Responds. n The following excerpts are from
p. 28.
I hasten to point out that data from a number of carefully
done conmercial seedings strongly suggest that the person
who paid for the operation got a fair return on the
investment. In many other operations and experiments it
is impossible to lell. It really is somewhat 1ike going
to a physician when you are not feel ing well. You receive
an examination and a prescription and, if three days later
you feel better, you figure you got your money's worth.
But what if you do not feel better? \Iouldn't you spend some
more money on a reexamination, perhaps some x-rays, etc.? Not
infrequently, such reexaminations are helpful. Also, they can
cause a progress in medicine. From the point of view of cloud
seeding and of ·Our Need for a Policy Now· it seems regrettab'le
that Professor Batun failed to mention in the same article that
he performed a cloud seeding experiment lasting seven sunrners,
that his own evaluations of the first four-surrmer-long ·Program­indicated
301 less rain on days with seeding that on those
without, and that his own evaluations of the second ·Program· of
three SlIlIIler5 also indicated a 301 deficiency of rain on days
with seeding.
It seems to me that the above experience of Battan, as well
as that of the Tasmania experiment should not be prevented from
reaching the Federal Government and the public at large.
If they are broadly known, remedial studies are 1ikely to
follow leading to progress in science.
This is the end of my Addendum.
27
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REPORT DOCUMENTATION PAGE READI:-;STRtlCTIONS
BEFORE CO~IPl.ETlNG FORM
Jerzy Neyman
,. PER~QR"'NG ORGA"I >;AT'Q" "A"E ANO APORESS
Statistical Laboratory
Universit.y of California
Berkeley, CA 94720
Office of Naval Research
Washington, D.C. 20014
ONR NOOO 14 75 C 0159
\2 REPQRTOATE
November 1979
This document has been aporoved for public release; its distribution is
unlimited.
Slanted and unreliable
Weather modification technolo9,y
Tasmania exoeriment
Israeli exoeriment I
~rovide precision of results. Seeding
was interrupted -- or aborted -- whenever wind
directions suggested that Agt nuclei might be
conveyed directly toward a control area. (Since
such days were still counted as "seeded days," no
false significances would result.) In view of the
limited area offered by the interior of this large
island, remote-effect issues must. we feel, be
taken seriously. We do not feel cOl!lPetent to ad­equately
evaluate them here.
In the following pages there are described Minconsistencies"
of two different kinds. both occuring in the Wiorkowski-Odell
spedl issue No. 10. The focus is on two experiments, the Tasman­ian
and the Israeli experiments.
3. INTERFACE BETWEEN THE WORK OF WEATHER t()OIFICATION
EXPERIMEHTERS AND THAT OF STATISTiCIANS
The title of this section is based on a sentence in the Intro­duction
to the article by LJ. Smith (pp. 955-973), under the inspir­ing
title MAn experimenter's view of the application of statistics to
cloUd-seeding experiments." The spirit of the article seems to be
properly sUllITlarized by the dictum that "both the statistician and ex­perimenter
are searching for the truth as to what the cloud seeding
does. "
I fully agree with this spirit, but must suggest a change in
the fonnulation of the dictum. r~y preference ;s for the following:
"both the statistician and the experimenter OUGHT to search for the
truth as to what the cloud seeding does."
Unfortunately, such an interdisciplinary cooperation does not
always occur with the result that "much of the contemporary litera­ture
... is SLANTED AND UflRELIABLE."
While the motivation for cheating is, clearly, some personal
gain, the means used by particular experimenters may be complicated.
In fact, it may be subconscious. From the point of view of the
development of a reliable weather modification technology, the fol­lowing
passage from (Neyman, 1977a) is relevant:
RELIABLE INFORAATION ON EFFECTS OF
CLOUD SEEDING MAY RESULT FROM STRICTLY
RANOOHIZED EXPERIMEtrrS
With reference to precipitation augmentation, the
essence of a randomized experiment is, briefly,
as follows:
"se:~~~~'o~~~~~~~~~e~~~e~~~~:l-~~~~~;e(~~riable-are
clearly defined. In the simplest case, the po­tential
experimental period may be of fixed duration,
say 24 hr from 0730 of a gi ven day to 0730 of the
next. In this case, the response variable might be
the precipitation measured by specified gauges (de­fining
the "target"), say from 0800 of the given day
to 0800 of the next.
A special organizational unit, to be called the
"randomization center" (RC). must be established.
At an appointed time before the beginning of a po­tential
experimental period, the experimenter re­ports
to the RC whether the approaching potential
experilnental period is suitable for inclusion in the
experillll2nt -- that is, whether it is to become an
"experimental unit. - In the affirmative case, the
experimenter comnunicates to the RC certain other in­formation
deemed imoortant, such as the nature of the
prevailing weather (type A, type a, or type C, etc.).
In response, the RC provides the experimenter with a
randomized decision, either a permissive "seed" or a
categoric "do not seed." It is emphasized that the
randomized decision must be comflRJnicated to the ex­perimenter
AFTER his declaration as to the approaching
experimental unit, not before. In fact, it would be
best to arrange that even the personnel of the RC
have no advance information on the nature of the forth­comi
ng randOl!lized decision. Perhaps, a computerized
random nUl'Jt)er generator could be adjusted for this
purpose ....
The primary evaluation of the experiment must be
based on all the experimental units (some seeded
and others not) and no others, and it must use the
originally defined response variable. The supple­mental
information about the type of weather ought
to be used for stratification purposes and is use­ful
by providing the experil!'lenter with lreans to
verify his ideas.
The reader will realize that the spirit of the above passage
is fully consistent with Dr. Smith's idea that "both the statistician
and the experimenter are searching for the truth as to what the cloud
seeding does."
As ell19hasized by Smith, the experimenter has a specific field
of competence "in subjects suchas physics, meteorology" [perhaps,
also] "aviation and engineering.- The type of experiments contem­plated
by Smith is exemplified by the Tasmania experiment analyzed
by Miller !!....!.!.' p. 1017 1n the same issue of COJIIDunications in
Statistics. The object "of the experiment is to find out if seed­ing
cloudS with ice nuclei can increase the rain MEASUREO OVER A
DESIGNATED TARGET AREA [emphasis added]. Time is divided into .per­iods
[which I shall assume to be one day] on some of which selected
at random, seeding takes place ... " The statistician is expected to
analyze the data reliably, in order to answer the questions of the
experimenter and, possibly, also those of his "customer" such as a
hydro-e1ectri c author; ty.
Quite rightly, Smith is uneasy about the assumptions underlying
the statistician's work. "The objective ought to be to avoid the
use of any assunption unless there is good evidence that it is
acceptable." I fully agree. Specifically, a statistician's "reli­able
assumptions" are proved theorems, such as the law of large num­bers,
the central limit theorem, etc. Provided there are no mistakes
in the deductions, the conclusions drawn using such theorems wilT be
reliable (Neyman, 1979a).
My own concern is that, in addition to hypotheses underlying
the work of the statisticians, there are also hypotheses adopted by
the experill'lentalists. Are they always realistic? Here is an example.
At the end pararaph of Smith's Introduction there is the follow­ing
outline of a proposed method of analyzing the data of a randomized
experiment:
For each seeding day the ll'lE'asured tarQet area
rainfall is compared with an estimate of the
rain that would have fallen in the same period
if seeding had no effect. This estimated rain
is derived from covariates which usually include
rain in adjacent control areas in both seeded
and unseeded periods. (In simple experiments
the measured rain in a control area may be used
as an estimate).
It is here that I see a contradiction between the opinion of
Dr. E.J. Smith and my own. It seems to me that the methodology in­dicated
by Smith depends upon an unverified hypothesis, a "meteoro­logical"
hypothesis, that seeding over the designated target does
not affect the rainfall in the adjacent control area. Otherwise,
-the measured rain 1n a control area" during a seeding period would
not be an appropriate estimate of the target rainfall "that would
have ,fallen in the same period if seeding had no effect. II
In full confonnity with Smith's own suggestion that -the ob­jective
ought to be to avoid the use of any assulTlltion unless there
is good evidence that it is acceptable," I feel in need of an effort
at verification.
How can one check, at least tentatively. whether the ass~tion
that the rainfall in a control area is not affected by seeding over
the target? How can one do so without relying on any other unveri­fied
asswnption? The only answer seems to be: examine the totality
of published experimental data and produce a sUlllllary.
The data on the Tasmania experiment we have were published two
years ago (Smith!!....!!.. 1977). There are two sets of data. Both
give average rainfall arr(lunts in the intended "target" and in four
other areas in Tasmania. Three of them are described as "controls"
and the fourth as the Eastern Subsidiary Area, see Figures land 2.
The precipitation amounts are means per raingage, per "period."
The particular perioe's varied in length, from about ten to eiohteen
days. As i ndi cated in the above quotat; on from the report of the
Statistical Task Force, there were some irregularities.
One set of data refers to four years 1964, 1966, 1968 and 1970
which were the experimental years, with seeding over the target dur­ing
randomized periods. The other set of data refers to years 1965,
1967 and 1969 during which rainfall amounts were measured in all the
five areas but there was no seeding. We may label these years, the
"control years." The purpose of the three "odd" control years inter-mingled
among the four "even" experimental years was to check the
hypothesis, again a meteorological hypothesis, that the seeding dur­ing
a particular year can affect the precipitation during the subse­quent
year, the so-called "presistence" hypothesis.
The attempt at an objective sunmary of all the publlsbed precip­itation
data resulted in Figures 1 and 2. Both show the map of Tas­mania,
including the target and four other areas mentioned. The
Stat. Lab's contribution is limited to percentages attached to each
of the areas of interest. They represent what I like to label "per­cent
effect" of seeding, namely 100[{S-NSl/NS]. Here Sand NS repre­sent
the mean measured rain in the given area that fell during the
periods with and without seeding, respectively.
Figure 1 corresponds to the four experimental years, 1964, 1966,
1968 and 1970. It is seen that the percent effect in all the five
areas is negative. The least seed period deficiency of rain, namely
8%, was found for the target and for the "South Control" area. The
greatest seed period deficiency was found for the North Control. It
amounts to 21%, more than double that for the targetl The deficiency
of seed period rain for all the areas corrbined is 15%, a finding
likely to be of interest to the hydro-electric authority.
What is convincing and what is not is a subjective matter. In
my own opinion, Figure 1 fails to support the assumption that seeding
over the target does not affect the rain over the North Control. If
anything, it seems to support the idea that seeding by methods com­parable
to those in Tasmania can have far-away effects that are strong­er
than those in the target. See Section 2 above.
LOCATION OF TARGET
AND CONTROL AREAS
Roinoouqee
Airport t:.
o NOUljC;~ Mile$40
~:"':~,
NORTH- eORTHCONTROL co'%1lbl· -:.: A2R!~A AREA •• ". Lounceston
-14% •• EASTERN
TARWET SUBSIOlARf
42" ~:iA ••: ~ •• ~;5~o ..- ...
145" 148"
FIG. 1. Relating to experimental years.
LOCATION OF TARGET
AND CONTROL AREAS
FIG. 2. Relating to control years.
Here. with some feeling of regret. I must mention II point relat­ing
to the statistical team that cooperated with Or. Smith in the
evaluation of the Tasmania experiment. As indicated on p. 1021,
the team used the "dolble ratio statistic," because it "has an intu­itive
appeal." The reader will have no difficulty in noticing that
this "intuitive appeal" depends very much on the unYeri fled "meteor­ological"
hypothesis that the seeding over the target does not af­fect
the rain in the control. In particular, if the effects of seed­ing
on rain in the target and in the control /Ire both negative and
if the negative effect in the control is stronger than in the target
(as in Figure 1), then the double ratio statistic will lead to II
misleading conclusion.
It seems to me that the selection of a test statistic merely
because of an "intuitive appeal" is not an inspiring procedure. The
roore challenging way is to formulate sorr.e intelligible optimality of
the needed test criterion and to DEDUCE the needed formula (Neyman.
1979a).
Figure 2. analogous to Figure 1. illustrates the precipitation
pattern in Tasmania that prevailed during the three control years.
when there was no seediny. Here. the "percent effects" were calcu­lated
for·what may be labeled "placebo seeding." As mentioned. the
ptblished data give the rainfall alOOunts for consecutive periods.
The succession of "placebo seeding" was arranged to coincide with
the succession of real seeding for the experirental years. It is
seen that the patterns of rainfall exhibited 1n Figures 1 and 2 are
very different. Is this difference causally related to seeding dur­ing
the experimental years and to the absence of seeding during the
controls? Not necessarily. It R"lay be due to rrr; mistak.en allocation
of "placebo seeding" during the control years.
The essence of the presistence hypothesis seems to be that.
whatever the effect of seeding in a given year may be. this effect
"persists" over several months of the next year with a gradual decay.
Here we face a difficulty that seems even greater than that in the
establishment of the phenomenon of the far-away effects of local
10
seeding. The point is that the possible "persistence" effect is
confounded with faMiliar seasonal variation in precipitation. In
very general terms, the Berkeley area has two rainy periods, of
about one month duration. One, a mild one, occurs in October­Novemer,
and the other, stronger one, begins about the middle of
January. Naturally. the intensity of these rainy periods varies
considerably from year to year.
4. ILLUSTRATIONS OF FAR-AWAY APPARENT
EFFECTS OF LOCAL SEEDING FOUND ELSEWHERE
During our more than a quarter of a century of interest in
weather modification, it was natural for our Berkeley group to
study the reliability of experimental designs that were corrmonly
used. This included the cross-over design and the design using
control areas. We found them both unreliable. The relevant ques­tion
was whether the seeding over the designated target can affect
the rainfall over a distant area.
Experilrents suitable for studying this question are those of
long duration, with a properly randomized design of seed/no seed
over a designated target and with a "natural" experimental unit of
24 hrs, morning to morning. Here, the word "natural" refers to the
periodic changes in temperature, etc., connected with the irradiation
from the sun. The additional requirements refer to the availability
of data on wind directions and on hourly precipitation data.
Our studies included three experiments: (1) the Swiss experi­ment
Grossversuch III, (2) the Whitetop experiment of Professor R.R.
Braham performed in Missouri, and (3) the Arizona experiment performed
by Professor Louis J. Battan. To my regret (Neyman, 1979b), a closer
study of the Whitetop experilrent indicated some difficulties with
randomization. For this reason, the findings described below refer
to two experiments only, the Grossversuch III and the Arizona exper­iments.
The details of the work are somewhat voluminous (see refer­ences
quoted below) and the following brief SUrMlaries must suffice.
The far-away effects of local cloud seeding werE:' first studied
for the Swiss experiment Grossversuch III (Neyman ~, 1969).
11
Here, the target was the canton T;eino on the southern slopes of
the Alps. The studied far-away localities included two areas in
Switzerland in which we had reliable data from 20 gages each. One
area was near Z'urich (some 80 miles away) and the other near Neueh­atel
(some 120 miles away). The average apparent effects of seeding
on all the 190 days with "stability layers" were as follows:
Table I
Apparent effects of seeding at Grossversuch III
on days with stability layers
12
Area
Tieino
Zurich
Neuchatel
Percent Two-tail
Effect Significance Probability
+£4 0.031
+67 0.012
+57 0.037
As mentioned, Table r refers to all the 190 days, irrespective
of the prevailing wind directions. The followin9 Table II gives sim­ilar
data for the 94 days when the published winds had a southerly
velocity component. This stratification was performed because of the
information that the primary source of atroospheric humidity in Swit­zerland
is the Mediterranean, in the south.
Table II
Apparent effects of seeding at Grossversuch III
on days with stability layers and southerly winds
Area
Ticino
Zurich
Neuchatel
Percent Two-tail
Effect Si gniti cance-Probabil ity
+102 O.OlB
+116 0.004
+ 64 0.060
In interpreting this table one must remerrber that Zurich is al­most
directly north of Ticino while Neuchatel is substantially to the
northwest. Here, then, the degree of "downwindedness" was crude,
which stimulated the development of a new methodology, the moving
grid methodology (Lovasich ~. 1971).
Curiously, the apparent effects of seeding on days with uninhib­ited
updrafts were all negati ....e. but none significant by customary
standards. The subsequent use of the moving grid methodology clari­fied
the situation. The original measurement of the degree of down­windedness
was too crude. Our final finding was a 61: average defi­ciency
of seeded day precipitation in localities 90 to 180 miles down­wind
from Tieino. with a two-tail significance p" 0.002.
The above findings for Grossversuch III were unexpected and stim­ulated
our interest in the question of the generallty of the phenomena
observed. It is this question that rot'ivated our persistent'studies
of the Arizona experiment performed by Professor l.J. Battan. The ex­periment,
with two "programs." included 212 experllllental days. Profes­sor
Battan's target was an isolated body of Santa Catalina Mountains.
The seeding was conducted over2-4hours beginning at about 12:30 p.lIl.
Battan's own evaluation was based on rainfall during 5 hours only. from
1 p.m. to 6 p.m. Our reevaluation used 24 hour rainfall from noon to
It included not only the Santa Catalina Mountains but also a
locality. Walnut Gulch. about 65 miles to the south soutbellst from the
Santa Catalinas. Here. the Water Conservation Research Division of
the Agricultural Research Service maintains a very tight set of re­cording
rain gages. The person in charge is Dr. Herbert B. Osborn.
It appeared that during the Arizona experiment there were 26 gages
that operated reliably. Table III surtrnarizes the results obtained
(Heyman!!.....!!.. 1972).
Table III
Apparent effects of seeding at the Arizona experiment
13
locality
All Davs
Percent Two-tail
Effect Probability
Walnut Gulch Downwind
Percent Two-tail
Effect Probability
Santa Catalina
Walnut Gulch
-30
-40
0.06
0.02
-9
-73
0.78
0.01
It ;s seen that both parts of Table III indicate the apparent
effects of seeding over the Santa Catalinas on the 24 hour rain at
Walnut Gulch are stronger than in the intended target. Also. the
significance of these effects is rrore impressive.
The timing of these apparent far-away effects is of interest
(Neyman, 1977a). It is illustrated in Figures 3 and 4.
FIG. 3. Diurnal variation in hourly rainfall in Zurich when it was
approximately downwind and when it was approximately upwind
from Tieino. Solid lines correspond to days with seeding;
dashed lines to control days.
ii 4. T,_.",
FIG. 4. Diurnal variation in hourly rainfall in Walnut Gulch when it
was approximately downwind and when it was approximately up~
wind from the Santa Catalinas. Solid lines correspond to
days with seeding; dashed lines to control days.
It would he J!()st interesting to see whether the "downwind/up'Hind"
differences illustrated in Figures 3 and 4 were also observable during
the Tasmania experiment. The difficulty is that 1n Tasmania the exper­imental
periods were rather long, presumably with very variable wind
directions, with varying wind velocities, etc.
14
5. COMPARISON WITH THE ISRAELI EXPERIMENT I
It is my opinion that the Tasmania experiment, as dt!scribed in
the Wiorkowski-Odell special issue of COrM1unications in Statistics,
and especially as described in the Final Reoort (Smith ~. 1977).
;s a very valuable contribution to the weather modification litera­ture.
The reason is that the material published includes many de­tails
about the facts that happened, the facts relevant to Dr.
Smith's question about "what the cloud seeding does." r wish I
could express a similar opinion on the Israeli experiment. This
applies both to the original evaluation (Gabriel, 1967) and to Pro­fessor
Gabriel's article in the Wiorkowski-Odell special issue now
discussed. The following passages, marked A and B, are quoted from
this article.
A. Page 983.
Pemaps one reason for the surprisin9 success of the two
Israeli experiments is that expertise in cloud physics
was closely involved in all stages of design, evaluation
and analysis (Gabriel, 1967; Gagin and Neumann, 1976).
In the existing uncertain state of the art, we cannot
afford to do without the very best available experts.
B. Page 977.
In the first Israeli experiment (Gabriel, 1967), the ex­perimental
unit was a 24-hour period, STARTING AT 8 AND
ENDING AT B on the next day. (1) Randomization was applied
to calendar dates and ...
The reader will notice that the above capitalized description
of the experimental unit is not complete. The hour 8 may be B a.m.
or B p.m. The following passages, marked C and D, are quoted from
Professor Gabriel's article, described as (Gabriel, 1967).
C. Title Page.
THE ISRAELI ARTIFICIAL RAINFALL
STIMULATION EXPERIMENT.
STATISTICAL EVALUATION FOR THE
PERIOO 1961-65
K.R. Gabriel
Hebrew University, Jerusalem
15
1. Introduction
A rainfall stimulation experiment is being carried out
in ISrael by silver iodide seeding from an aircraft in a
randomized crossover design. The operations are directed
by Electrical and Mechanical Services (Mekorot, ltd.),
Mr. H. Cohen, Director, and are financed by the Israeli
Ministry of Agriculture. The experiment is conducted
under the guidance of the Rainfall COll1llittee whose chair­In3n
is Professor LD. Bergmann, and the related research
work. is performed at the Hebrew University, under the direc­tion
of Professor J. Neumann. THE AUTHOR IS RESPONSIBLE FOR
THE STATISTICAL DESIGN AND EVALUATION, Daily rainfall data
are provided by the Israeli Meteorological Service from its
regular network of raingage stations. [Emphasis added.]
O. Page 94. Table specifying the experimental units on which
the evaluation was based.
TABLE II
~ITS EMPLOYED IN THE EXPERIMEKT
Season Date Period Unit of Time
1961 half 19. 2.61-15. 4.61 weekly 0000 to 0000 hrs
15.10.61- 5.11.61
1961-62 7.11.61-15. 4.62 daily 2000 to 2000 hrs
1962-63 16.10.62-15. 4.63 daily . 2000 to 2000 hrs
1963-64a 1.11.63- 8. 1.64 daily 2000 to 2000 hrs
1963-64b 9. 1.64-lJ. 4.64 daily 0000 to 0000 hrs
1964-65 16.10.64-15. 4.65 daily 0800 to 0800 hrs
Here the specification of the experimental units is complete.
H"""ever, it is indicated that the actual units varied. For a brief
period the unit was 8 a.m. to 8 a.m. Then, for a longish period, it
was from 8 p.m. to 8 p.JIl. Then there was a return to the original
8 a.m. to 8 a.m. This description generated some literature.
1 felt impressed by the variability of the experimental units,
and when writing a historical review (Neyman, 1977b), expressed the
opinion that the design and the evaluation used are "unprecedented."
Next year there appeared two protests (Gabriel and Neumann, 1978) and
(Mielke, 1978). Here it is relevant that Or. Hielke, a Professor of
Statistics, is at least partly responsible for the evaluation of the
cloud seeding experiment known as Climax I. This evaluation is also
mentioned in (Neyman, 1977b).
16
17
Here, I wish to refer to the statement by the Editors Wiorkowsi­Odell
that their Special Issue was complied so that the statistics
cOFmlunity could gain insight into the complexities of weather II"()difi­cation
studies. My suggestion is that interested rrembers of the sta­tistics
cOlMlunity examine the publications mentioned in the preceding
paragraph. In fact. I wish to suggest one IOOre paper (Hobbs and Rang­~~.
This paper ends with the following sentence:
"In view of the irrportance that has been placed on
the Climx results, an independent evaluation of the
statistical results of these experiments is urgently
needed. "
My question is: Why only of Climax?
ACKNOWLEGEMENTS
This article was prepared using the facilities of the Statistical
laboratory, with partial support from the Office of Haval Research,
Contract No. ONR NOOO14 75 C 0159, and the DepartlU!:nt of the Amy,
Grant No. OA AG 29 76 G0167. All the opinions expressed are those
of the author.
BIBlIOGARPHY
Cleveland, Harlan (1978). The ManagelU!:nt of Weather Resources,l, Pro­posals
for a National POllCY and Program, Report to the Secretary
of COllJl1erce from the Weather Modlftcatlon Advisory Board (Harlan
Cleveland, chairman); II, The Role of Statistics in Weather Re­sources
Management, Report of the StatlsticaJ task Force (JOhn W.
lukey, chainnan) to the Weather Modification Advisory Board.
Washington, D.C.: U.S. Government Printing Office.
Gabriel. K.R. (1967). The Israeli rainfall stilllulation experiment,
statistical evaluation for the period 1961-65. Prot. Fifth Berke­lev
SYIIlJ). Math. Stat and Prob., ::!..' "'leather Modlflcation (luclen
Le Cam and Jerzy Neyman, editors). Berkeley: University of Cal­ifornia
Press, 91-113.
Gabriel, K.R. and Neumann, J. (1978). A note of explanation on the
1961-67 Israeli rainfall stimulation experirrent. J. Appl. Meteor.,
.!l.552-554.
Hobbs, Peter V. and Rangno. Arthur L. (1979). COn'll'lE!nts on the Climax
and Wolf Creek Pass cloud seeding experi~nts. J. App1. Meteor.,
.1!. 1233-1237.
Lovasich. J.l. , Neyman, J., Scott, E.l. and Wells, M.A. (1971).
Further studies of the Whi tetap cloud seeding experiment. Proc.
Nat'l Acad. Sci., §!. 147-151. -
Mielke. Jr., Paul W. (1978). On criticisms concerning the Israeli
experiment. J. Appl. Heteor .• .!l.. 555-556.
Neyman, J. (1977a). A statistici.a,n's view of weather ll'IOdification
technology (a review). Prot. Nat'l Acad. Scf.l!. 4714-4721.
Neyman, J. (l977b). Experimentation with weather control and statis­tical
problems generated by it. Applications of Statistics
(P.R. Krishnaiah. ed.). Amsterdam: North-Rolland piblishing
Co., 1-25.
Neyman, J. (1979a). Developments in probability and mathematical
statistics generated by studies in meteorology and weather mod­ification.
COl'l'l1lun. Statist.-Theor. Meth .• ~. 1097-1110.
Neyman. J. (1979b). COll11lent on Professor Braham's paper "Field Ex­periJrentation
1n Weather Modification." J.A.S.A .• Ii. 90-94.
Neyman J. and Osborn. H.B. (1971). E.... idence of widespread effects of
cloud seeding at two Arizona experiments. Proc. Nat'l Acad.
Sci .• ~. 649·652.
Neyman. J .• Scott. E.l .• and Wells. M.A. (1969). Statistics in rreteor­ology.
Rev. tnt'] Stat. lnst .• E. 119-148.
Neyman. J .• Osborn. H.B .• Scott. LL.. and Wells. M.A. (1972). Re­evaluation
of the Arizona cloud-seeding experiment. Proc. tlat'l
Acad. Sci .• §!. 1343-1352. ----
Smith. E.J .• Veitch. loG .• Shaw. D.E.. and Miller. A.J. (1977). ~
Cloud-Seeding EXJjerirnent in Taslllania. Final Re~rt. Part 1.
~es~;~~ihoSc~~~tti~~ :~dU;~~~st~~~~s ~~e~~J Ig~a~~~~~~~~.Com-
Australia.
18
I am indebted to Professor David R. Brillinger for call iog my
attention to the relatively brief paper by Harlan Cleveland and
for providing me with a copy. Weather lilOdification issues are
complex and, in 11 sense, Cleveland's paper is revealing. It is
likely to be useful not only to the editors W;orko~lski and Odell.
but also to the public at large. Because Cleveland's paper repre­sents
his testiroony before a group of- U.S. Senators, its circula­tion
must be limited. It is reproduced in the present Addendun.
THE 1'IAHAGE.lIIENT OF WEATHER RESOURCES:
Our Need for 11 Pol icy is Now
Testimony of
Harlan Cleveland
Chaiman of the Weather Modification Advisory Board
before the
Senate Corrmittee on Corrmerce. Science and Transportation
SubcollJDittee on Science. Technology. and Space
October 24. 1979
Aspen Institute for Humanistic Studies
Pro9ram in International Affairs
P.O. 80x 2820. Princeton, N.J. 08540
THE "'.ANAG£MEHT OF WE!HHER R£SORUCES:
Our Heed for a POlley lS Row
Testi1T.Onyof
Harlan Cleveland
Mr. Chairman:
1.
In the Hational Weather Modification Polley Act of
1976 (P.L. 94-490 of October 13. 1976). Congress called
on the Secretary of Cor.merce to ~conduct a comprehensive
investigation and study of the state of scientific know­ledge
concerning weather modification technology. the
problems 'impeding effective implementation of weather
modification technology, and other related matters."
The study was ~to develop a comprehensive and coordinat­ed
national weather rodification policy and a national
program of weather modi fi cation research and development.·
Congress asked for a final reoort in one year.
It is now three years and eleven days later. A
part of that time -- a little more than a year of it --
19
was occupied by the work of the Weather Modification Ad­visory
Soard, which was appointed by Secretary of Corrmerce
Juanita Kreps in April 1977. held twelve publ ic hearings
and working meetings in various parts of the United States.
consulted ....ith experts frolll many other countries, and sub­mitted
its final report to the Secretary on July 12, 1978.
This report, entitled The Management of Weather Re­sources:
Proposals for a National Policy and Program, has
of course been aVill lable to the Congress as well, but the
Executive Branch had not until this hearing reacted to the
report or expressed itsel f on the need for a national pol­icy
about efforts to change the weather at hUl!Ian corrmand.
/o':eanwhile two bills to establish a national policy and
authorize a national program have been introduced, S.1644
by Senator Adlai Stevenson and S.829 by Senator Bellman.
You have asked me, as Chainnan of the now~disestab­lished
Weather ~odification Advisory Board, to discuss
these bills. without advance notice of the position, if
any, of the E;.lecutive Branch.
The Advisory Board's report contains a rather full
SUlIJMry and Recommendations. That section of the report
was reproduced in full in the October 1978 issue of the
~~iJe:ifo~:W~~~ ~~~~~~ 7e;=~~i~daih;o6~~~f'b~ig~~:~_
sive administrative history of the Advisory Board and iden­tified
its members. A reprint of this material is attached
to my testimony. Rather than burden my direct testimony
by rehearsing 1n detail the arguments and conclusions in
our Report, I would hope that the SUflIConmittee would be
willing to include in the record of its hearing the text
of this reprint.
II.
I think it is fair to say that the unanimous report of
our Advisory Board is the most comprehensive policy analysis
now available on the subject of weather modification -- or
weather resources management. as we preferred to call it.
It may be helpful to Ilighlight our key findings and propos­als.
First. The benefits likely to be derived fmlll man­agement"
01 weather resources -- for the" distribution of water,
the growing of food and fiber. the production and conserva­tion
of energy, and the warding off of some of the severest
storms -- are out of all proportion to what it will cost to
learn enough about the atmosphere to modi f.v the weather pur­posefully
and prudently.
Second. The prime reouirement of a national policy in
this ~is to learn ll'lOre about the atmosphere itself.
But we know enough already to guess that a IOOch intensified
and steady program of scientific inquiry and field experi­ments
over the next two decades will yield regionally
20
important increases in mountain snowpack in the early 19805,
increased rainfall in areas like our High Plains in the late
19805, and reduced hurricane winds and hail damage by the
19905.
The scientific uncertainties are real. But they are not
a reason for the Federal Goverrwent to freeze in hand-wring­ing
inaction. They are also not a reason for the scientific
. cOl!1llUnity to acquiesce in inaction. If they were, uncer­tainty
would have ruled out the experiments of Galileo, the
explorations of Columbus, and even the speculations of
Heisenberg on uncertainty. The proper attitude toward
scientific uncertainties that stand in the way of large
potential benefits to farmers, city people and dwellers on
hurricane-prone coastlines ;s to get on with a serious
research and develo!Xflent effort that matches the scale and
complexity of the problem. And the key to such an effort. as
we said in our report. is basic research on the physics and
dynamics of the atmosphere itself.
Third. The main weather modification technology. cloud
seediiig'Tilsually with silver iodide), has been used
OPERATIONALLY in 74 countries and is regularly practiced in
the United States. [Emohasis added.] In 1977 clouds were
seeded in 88 projects in 23 states, coverin9 more than a
quarter of a llIillion square miles of U.S. territory. The
Federal Government, working with the states. has to assume
responsibility for making sure that quality standards and
qual Hied people are the rule in weather resources
management.
Fourth. Most "weather modification" so far has been
unint~ the product of urbanization. power production.
cropping patterns. deforestation and irrigation. Learning
roore about the unintended consequences of modern industrial
civilization is an essential part of learning how to change
weather on purpose in ways that benefit people.
Fifth. More and more Americans are moving into hurri­cane
patJi'S; the U.S. migration to the Sunbelt has enormously
increased the populations, property and productive industry
at risk. Even on faVOrable assumptions about warning times.
another storm like 1969's Camille. roving up the sea-level
delta from Galveston to Houston. could cost 10,000 lives and
inundate two-thirds of the U.S. petrochemical industry in a
few hours.
Hurricanes are a triple threat --: from wind, .stonn surge
and flooding. There is an intriguing but not yet proven
theory for moderation of their wind speeds. but it needs a
sustained U.S. research effort and a sensitive framework of
international cooperation. especially to facilitate experi­ments
on real hurricanes in the Western Pacific.
The Weather Modification Advisory Board last year
proposed a lO-year test of hurricane IOOderation, which might
cost S8 to SlS million a year. The recOI:JJlendation is still
21
resting in an Executive pi"geonhole. Do we really need
to have a couple of billion-dollar, kilodeath storms to
spur us fnto doing our scientific and technical homework
on the most devastating kinds of weather?
Shth. Weather resources mani!nernent is, in effect,
a delTIi'e'r"ate "environmental impact;;' so environmental
considerations have to be part of the planning of every
weather apdification try. So does the analysis of eco­nomic
costs and benefits. And so do arranQements for
making sure the affected publics know What-is planned,
and have a chance to help decide what will be done. As
our report says, ~There is no area of public affairs
where a policy of official candor is more integral to
the success of a Government-sponsored research-and-devel­opment
prtlgram. ~
Seventh. The Federal Governn>ent has broad responsi­bilit~
uman intervention in weather systems that do
not respect state, or indeed national frontiers. But
weather resources management is still a very small indus­try,
and we did not propose to lay a heavy regulatory
glove on it. We did make these suggestions:
(a) Each weather management operator should have
a Federal license, as aircraft pilots do.
(b) The Federal Government should take responsibil­ity
for issuing continuously updated, environmentally sen­sitive
·Sound \o,Ieather Resources "'.anagement Practices,"
based on state-of-the-art technology. These would serve
both as a standard to which all Federal field experinents
WOUTd be held, and as guidance for state regulators,
weather resourcemanagers, user organizations such as
farm groups, courts and arbitrators.
(cl The Federal Government should arrange to pro­vide
technical assistance in weather resources managment
to states, local authorities, and private users and oper­ators.
(d) The Federal Government should make clear that
its own operations are subject to claims for damage under
the Federal Tort Claims Act.
~. The United States should actively promote
internatl0nal consultation and cooperation in the field of
weather modification. The benefits of close and candid
consultation are two-way. We want to make sure that our
own programs benefit from the discoveries, insights and ex­periments
of others. And we want to assist other countries
to increase their food, water and energy supplies and limit
their weather damage. To make clear that the U.S. intent
is to prOlll)te the peaceful uses of weather IIX)di fication, our
Advisory Soard also recOfi11lended the earlv ratification of
the EnvirOl'lllental f40dification Convention, a treaty already
signed by the U.S.
22
Ninth. We recomnended a sustained 20·year program of
researcFi""and development, including basic research; refine­ment
of cloud seeding techniques; experiments in the dissi­pation
of stratus; a special effort to learn roore about warm
fog; the study of atmospheric responses to land use, fann
practices, industrial processes and urban 1ife; a special
push to develop techniques for reducing peak winds in
hurricanes; support for the first international cloud-seeding
experiment, now being actively phnned; research on ways
other than cloud seeding to modify local Iveather; research on
impacts -- environmental, economic, and social -- of weather
resource management; and a cooperative Federal/State local
effort to garner maximum scientific knowledge from selected
OPERATIONAL cloud-seeding projects. [Emphasis added.]
The recorrmended R & 0 effort, containing all elements,
would call for Federal appropriations of $37 million in the
first program year (roughly twice the 1977 total of Federal
agency spending for comparable purposes), and increases to
$90 million in the fifth year.
Tenth. The Advisory Board recomnended the consolidation
of alltFi'e Federal GoverlV:lent's weather modification work in
one organization and sufficient autonomy for that organiza­tion
to produce. defend, and carry out a serious and consis­tent
long·term program of research and development .. and
handle the minimal regulatory functions in a highly profes­sional
way.
III.
The members of the Advisory Board were not born yester­day.
We knew how difficult it is in our big government to
"get it all together," how vigorously defended is every
square inch of existing bureaucratic turf. and how hard it is
in every field of public policy to sell integrated and pur­poseful
action to constituencies which perceive a stake in
fragmented action programs. But we were asked to propose a
national policy and program, and we were unan~mous in
concluding that a consolidated program is a must.
I hear tell that even some of the most vigorous
supporters of a serious weather modification effort are now
prepared to settle for a pattern of continued fragmentation.
with some 1im; ted national planning and coordination
attempted through a "lead agency." I believe that this would
be a mistake. "Lead agency" in U.S. federal experience;is a
euphemism for not getting thin')s organized so they are going
to work, yet pretending to do so. "In practice," we said in
our report, "a lead agency generally means telling one part
of the Executive establisl'ment to take charge without placing
in its hands the tools required for leadership."
Our proposal. a deliberately unusual one, was to
establish a small executive board with "a life of its
own" in an existing agency. and an executive director
to carry out the national policy to be enunciated by
Congress; and to bring into the new board's purview,
as its own staff or through contractual relationships,
all the Federal Governl!'!ent's existing and future weath­er
modification programs. This central organization
could and should delegate particular projects to the
agencies best able to carry them oUl; for example, an
experiment such as the bureau of Reclamation's HIPlEX
would logically be entrusted to the Bureau of Reclama­tion
to manage. within the framework of policy and stan­dards
established by the national program office.
Our consensus proposal a year ago was that this
function should be allocated to the National Oceanic and
Atmospheric Administration (NOAA) -- although some mem­bers
of the AdVisory Board would even then have opted for
NASA or even NSF as the host agency. The delay in react­ing
to our report raises -- let us say it frankly -­serious
questions about the capacity of NOAA to take the
kind of vigorous lead that would be required to get a
national weather manage~nt program pulled together and
up to speed.
My own feeling -- the Board has disbanded and I can­not
speak for its rnelTbership ~- is that the earl ier the
consolidation of oceanic and atmospheric functions in one
agency was an enorll'Ous step forward in organizing the
Federal Government for sensible management of resources
in these very special global environments. If NOAA is not
yet the effective center of initiative. Mt yet the enter~
prising and innovative agency it will have to become if it
is to serve our national interest. the proper rel!ledy is to
modify its management. not start stripping it of oceanic
and atJrospheric functions.
IV.
l~eanwhile, in the field of weather resources manage­lTlent,
we are still "taCkl1ng 20~year problems with 5-year
projects staffed by short-term contracts and funded by
one-year appropriations. It is not good enough.· That is
what we said to the Executive Branch more than a year ago,
and that I believe. is still essentially the state of affairs
today. I am therefore delighted that this subconmittee is
moving toward a legislative initiative.
Either of the bills you are considering would represent
a very large step forward from where we are. But as the
corrrnittee writes a bill to present to the Senate. you may
wish to coniline elements of both bills in the final draft.
24
• 5.829, for example. contains in its "Findings"
a rather fuller analysis of the present situa­tion,
and its "Policy" section is closer to the
recomnendations of the Weather Modification Ad­visory
Board. than the comparable formulations
in 5.1644.
• I would hope that the concept of Federal "Sound
Weather Resources Practices· could be a part of
the final draft; the professional quality of
weather resources rnanagel!lent is what will make it
possible to reap large benefits without running
large risks.
• The role of the States, and the need for Federal/
Stale/local cooperation, seems to me an essential
ingredient of a national policy and program;
this is lacking in $.1644 and perhaps not pointed
enough in S.829.
· The licensing of weather modifiers is provided for
in S.1644 but not in S.829; I would strongly re­cOJJlllend
that such a require«ent be retained in
the final bill. as an essential part of quality
control.
· Both bills provide for a board, but in both cases
it i~ advisory; I still think. a small executive
board, in which a few outstanding peoplecourcr­find
a vocation in nursing this potentially impor­tant
field of weather resources management from in­fancy
through adolescence during the next two or
three decades, is an idea worthy of serious con­sideration.
· Even if the board were to be adVisory, I would opt
for the smaller number of merrbers (6 as against lS)
and the longer terms of appointment (6 years rather
than 3), for reasons which do not need to be ex­plained
to any cOlMlittee of experienced political
leaders.
The k.ey functions of our proposed executive board and
its director, or of the Program's Director in the two bills
before you, should be the development of an integrated, roll­ing
five-year program, the management and allocation of the
financial resources which are placed at the disposal of the
national weather lIlOdification effort, and unremitting atten­tion
to quality control in both Federal and nonfederal weath­er
modification. I do urge the subcoJllllittee not to allocate
to a "lead agency" leadership responsibilities without the
administrative authority and budgetary tools to do the job.
v.
In my letter transmitting to the Secretary of COJmlerce
the report of the Weather Modification Advisory Board, in
the early sUl!l1'ler of 1978, I made one CClm1ent that may bear
2S
repeating now that your sub~comnittee ;s moving toward
action.
The history of our time is sprinkled with instances of
new technologies running ahead of the social, economic,
envirorr.:ental, international and institutional thinking
that should accompany them. Precisely because the science
and technology of weather resources Management are still
at such an early stage, there ;s an excellent chance in
this field to do things right •• that is, for policy to
be made and institutions to be bullt in parallel with the
scientific discoveries and technological innovations.
The United States of America does not have a national
policy for the management of \~eather resources. For
reasons spelled out in our report, our Advisory Board
(which was created in response to II Congressional initia­tive)
was una nino us in recor.mending that the time for
adopting II legislative policy stance, back.ing it with II
coherent executive program, and organizing seriously for
a longer term effort, is now.
The following details of the nicely fonnulated ·Testimony· of
Harlan Cleveland attract my attention. In his ·third highlight"
Harlan Cleveland infonns the Senators that "cloud seeding has
been used OPERAT.IOtlAllY [emphasis added] in 74 countries and is
regularly practiced in the United States. In 1977 clouds were
seeded in 88 projects in 23 states."
Again, in his "ninth highlight." Harlan Cleveland calls for a
20~year program ..... to garner maximum scientific k.nowledge frorn
operational cloud seeding projects." Also, he calls for "Federal
appropriations .. roughly twice the total of Federal agency
spending. "
Another point: while Chairman Cleveland found it necessary
to appoint a Statistical Task. Force, the need of statistical
analyses of already completed experiments (as contrasted with
·operations") does not seem to have been eI!lphasized to the Senate
Subconmittee on Science, Technology and Space. The ir.lplication
seems to be that, in the opinion of Chairman Cleveland, the
reanalysis of completed experiments, like the Tasmania and the
Climax experiments, is 1ikely to provide substantially less
"scientific knowledge" than studies of "operational cloud seeding
projects. "
26
Issues related to those discussed by Harlan Cleveland are the
subject of the voll,l'lle Legal and Scientific Uncertainties of
Ileather Modification (Ed .• W. A. Thomas, Duke University Press,
1977). Here, an article by Professor L. J. Battan is of particu­lar
interest. The article's title is -The Scientific Uncertain­ties:
A Scientist Responds. n The following excerpts are from
p. 28.
I hasten to point out that data from a number of carefully
done conmercial seedings strongly suggest that the person
who paid for the operation got a fair return on the
investment. In many other operations and experiments it
is impossible to lell. It really is somewhat 1ike going
to a physician when you are not feel ing well. You receive
an examination and a prescription and, if three days later
you feel better, you figure you got your money's worth.
But what if you do not feel better? \Iouldn't you spend some
more money on a reexamination, perhaps some x-rays, etc.? Not
infrequently, such reexaminations are helpful. Also, they can
cause a progress in medicine. From the point of view of cloud
seeding and of ·Our Need for a Policy Now· it seems regrettab'le
that Professor Batun failed to mention in the same article that
he performed a cloud seeding experiment lasting seven sunrners,
that his own evaluations of the first four-surrmer-long ·Program­indicated
301 less rain on days with seeding that on those
without, and that his own evaluations of the second ·Program· of
three SlIlIIler5 also indicated a 301 deficiency of rain on days
with seeding.
It seems to me that the above experience of Battan, as well
as that of the Tasmania experiment should not be prevented from
reaching the Federal Government and the public at large.
If they are broadly known, remedial studies are 1ikely to
follow leading to progress in science.
This is the end of my Addendum.
27
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